<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            width: 200px;
            height: 200px;
            padding: 20px;
            background-color: aliceblue;
            border-radius: 20px;
            display: flex;
            flex-wrap: wrap;
            align-content: space-between;
        }
        /* 原本的写法是这样 我之前好像是父元素的宽太大了，然后就第四个元素不会换行 */
        /* .box {
            display: flex;
            flex-wrap: wrap;
            align-content: space-between;
        } */
        
        .column {
            flex-basis: 100%;
            display: flex;
            justify-content: space-between;
        }
        
        .item {
            height: 50px;
            width: 50px;
            border-radius: 50%;
            background: black;
            display: block;
        }
        
        .item:nth-child(4) {
            /* align-self: flex-end; */
        }
    </style>
</head>

<body>
    <div class="box">
        <div class="column">
            <span class="item"></span>
            <span class="item"></span>
            <span class="item"></span>
        </div>

        <div class="column">
            <span class="item"></span>
            <span class="item"></span>
            <span class="item"></span>
        </div>

    </div>
</body>

</html>